Welding processes used for welding a workpiece in the form of a sheet, plate or the like includes: welding which utilizes a high-density energy beam such as a laser light and an electron beam, and arc welding such as MIG (Metal Inert Gas) welding and TIG (Tungsten Inert Gas) welding.
The welding with a high-density energy beam is a process in which density of energy applied to a workpiece is very high, and thus incorporates advantageous features such as a higher welding speed and a narrower width of a bead formed on the workpiece during the welding process.
In contrast, the arc welding is a process in which a larger amount of energy may be applied to a workpiece per unit of time, despite a lower welding speed, and may thus lend itself to welding of a thick plate. The arc welding also has the advantage of improved quality of a welded portion because a metal filler wire melts and thereby forms a collar on the welded portion.
In the welding utilizing a high-density energy beam, however, the ratio of spread versus penetration of the weld is smaller, and thus when thick plates were overlapped and welded together, a welded area of the workpieces would be so small that a desirable level of welding strength could not be secured on some occasions.
On the other hand, the arc welding would cause distortion of the weld to occur in some instances as a result of a great amount of energy applied; therefore, it should be noted that variations in the quality of welded surfaces might be produced by instability of arc discharge. Moreover, the arc welding also has the disadvantage of a lower welding speed.